How to Design SolarPV System &

What is a solar PVsystem?

Instal l a solar system and save as much as 50% off

the cost of e lectricity .

What is a solar PV system?Solar photovoltaic system or Solar power system is one of renewable

energy system which uses PV modules to convert sunlight into electricity.

The electricity generated can be either stored or used directly, fed back

into the grid line, or combined with one or more other electricity

generators or more renewable energy sources. Solar PV system is a very

reliable and clean source of electricity that can suit a wide range of

applications such as residence, industry, agriculture, livestock, etc.

Major system components

Solar PV system includes different components that should be selected

according to your system type, site location, and applications. The major

components for solar PV systems are solar charge controllers, inverters,

battery banks, auxiliary energy sources, and loads (appliances).

��� PV module � converts sunlight into DC electricity.

��� Solar charge controller � regulates the voltage and current coming

from the PV panels going to

the battery and prevents battery overcharging and prolongs the battery

life.

��� The inverter � converts the DC output of PV panels or wind turbines

into a clean AC current for AC

appliances or fed back into the grid line.

��� Battery � stores energy for supplying to electrical appliances when

there is a demand.

��� Load � is electrical appliances that are connected to solar PV

systems such as lights, radio, TV, computer,

refrigerator, etc.

��� Auxiliary energy sources - is a diesel generator or other renewable

energy source.

Solar PV system sizing

1. Determine power consumption demands

The first step in designing a solar PV system is to find out the total power

and energy consumption of all loads that need to be supplied by the solar

PV system as follows:

1.1 Calculate total Watt-hours per day for each appliance used.

Add the Watt-hours needed for all appliances together to get the total

Watt-hours per day which

must be delivered to the appliances.

1.2 Calculate total Watt-hours per day needed from the PV modules.

Multiply the total appliances Watt-hours per day times 1.3 (the energy lost

in the system) to get

the total Watt-hours per day which must be provided by the panels.

2. Size the PV modules

Different sizes of PV modules will produce different amounts of power. To

find out the sizing of PV module, the total peak watt produced needs. The

peak watt (Wp) produced depends on the size of the PV module and the

climate of the site location. We have to consider �the panel generation

factor� which is different in each site location. For Thailand, the panel

generation factor is 3.43. To determine the sizing of PV modules, calculate

as follows:

2.1 Calculate the total Watt-peak rating needed for PV modules

Divide the total Watt-hours per day needed from the PV modules (from

item 1.2) by 3.43 to get

the total Watt-peak rating needed for the PV panels needed to operate the

appliances.

2.2 Calculate the number of PV panels for the system

Divide the answer obtained in item 2.1 by the rated output Watt-peak of

the PV modules available to you. Increase any fractional part of the result

to the next highest full number and that will be the

a number of PV modules are required.

The result of the calculation is the minimum number of PV panels. If more

PV modules are installed, the system will perform better and battery life

will be improved. If fewer PV modules are used, the system may not work

at all during cloudy periods and battery life will be shortened.

3. Inverter sizing

An inverter is used in the system where AC power output is needed. The

input rating of the inverter should never be lower than the total watt of

appliances. The inverter must have the same nominal voltage as your

battery.

For stand-alone systems, the inverter must be large enough to handle the

total amount of Watts you will be using at one time. The inverter size

should be 25-30% bigger than the total Watts of appliances. In the case of

the appliance, type is motor or compressor then inverter size should be

minimum 3 times the capacity of those appliances and must be added to

the inverter capacity to handle surge current during starting.

For grid-tie systems or grid-connected systems, the input rating of the

inverter should be the same as the PV array rating to allow for safe and

efficient operation.

4. Battery sizing

The battery type recommended for use in a solar PV system is a deep cycle

battery. Deep cycle battery is specifically designed to be discharged to a

low energy level and rapid recharged or cycle charged and discharged day

after day for years. The battery should be large enough to store sufficient

energy to operate the appliances at night and on cloudy days. To find out

the size of the battery, calculate as follows:

4.1 Calculate total Watt-hours per day used by appliances.

4.2 Divide the total Watt-hours per day used by 0.85 for battery loss.

4.3 Divide the answer obtained in item 4.2 by 0.6 for depth of discharge.

4.4 Divide the answer obtained in item 4.3 by the nominal battery voltage.

4.5 Multiply the answer obtained in item 4.4 with days of autonomy (the

number of days that you

need the system to operate when there is no power produced by PV panels)

to get the required

Ampere-hour capacity of the deep-cycle battery.

Battery Capacity (Ah) = Total Watt-hours per day used by appliances x Days of

autonomy

(0.85 x 0.6 x nominal battery voltage)

5. Solar charge controller sizing

The solar charge controller is typically rated against Amperage and Voltage

capacities. Select the solar charge controller to match the voltage of the PV

array and batteries and then identify which type of solar charge controller

is right for your application. Make sure that the solar charge controller has

enough capacity to handle the current from the PV array.

The sizing of the controller depends on the total PV input current which is

delivered to the controller and also depends on PV panel configuration

(series or parallel configuration).

According to standard practice, the sizing of solar charge controller is to

take the short circuit current (Isc) of the PV array and multiply it by 1.3

Solar charge controller rating = Total short circuit current of PV array x 1.3

One 18 Watt fluorescent lamp with electronic ballast is used 4 hours

per day.

One 60 Watt fan is used for 2 hours per day.

One 75 Watt refrigerator that runs 24 hours per day with a compressor

run 12 hours and off 12 hours.

Example: A house has the following electrical appliance usage:

The system will be powered by a 12 Vdc, 110 Wp PV module.

1. Determine power consumption demands

Total appliance use = (18 W x 4 hours) + (60 W x 2 hours) + (75 W x 24 x 0.5

hours)

= 1,092 Wh/day

Total PV panels energy needed

= 1,092 x 1.3

= 1,419.6 Wh/day.

2. Size the PV panel

2.1 Total Wp of PV panel capacity

needed

= 1,419.6 / 3.4

= 413.9 Wp

2.2 Number of PV panels needed

= 413.9 / 110

= 3.76 modules

Actual requirement = 4 modules

So this system should be powered by at least 4 modules of 110 Wp PV

module.

3. Inverter sizing

Total Watt of all appliances = 18 + 60 + 75 = 153 W

For safety, the inverter should be considered 25-30% bigger size.

The inverter size should be about 190 W or greater.

4. Battery sizing

Total appliances use = (18 W x 4 hours) + (60 W x 2 hours) + (75 W x 12

hours)

Nominal battery voltage = 12 V

Days of autonomy = 3 days

Battery capacity = [(18 W x 4 hours) + (60 W x 2 hours) + (75 W x 12 hours)] x 3

(0.85 x 0.6 x 12)

Total Ampere-hours required 535.29 Ah

So the battery should be rated 12 V 600 Ah for 3-day autonomy.

5. Solar charge controller sizing

PV module specification

Pm = 110 Wp

Vm = 16.7 Vdc

Im = 6.6 A

Voc = 20.7 A

Isc = 7.5 A

Solar charge controller rating = (4 strings x 7.5 A) x 1.3 = 39 A

So the solar charge controller should be rated 40 A at 12 V or greater.

Conclusion:- Install a solar system and save as much as 50% off

the cost of electricity

.

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Contact USUNRIVALED SOLAR

7722 Pasadena, TX, USA 77503Phone: 346-808-0330

E-mail: info@unrivaledsolar.comwww.unrivaledsolar.com